A controlled red phosphorus@Ni–P core@shell nanostructure as an ultralong cycle-life and superior high-rate anode for sodium-ion batteries

Sodium-ion batteries (SIBs), a potential alternative to lithium ion batteries (LIBs), have attracted remarkable attention recently due to the natural abundance and low-cost of sodium. Here, we have presented a comprehensive study on combining electroless deposition with chemical dealloying to control the shell thickness and composition of a red phosphorus (RP)@Ni–P core@shell nanostructure as a high performance anode for SIBs. For the first time depending on regulating the dealloying time (1 h, 4 h, 8 h, 10 h and 20 h) of RP@Ni–P synthesized by electroless deposition of Ni on RP, 1 h RP@Ni–P, 4 h RP@Ni–P, 8 h RP@Ni–P, 10 h RP@Ni–P and 20 h RP@Ni–P with different shell thicknesses and compositions were prepared. The in situ generated Ni2P on RP particle surfaces can facilitate intimate contact between RP and a mechanically strong amorphous Ni–P outer shell with a high electronic conductivity, which ensures strong electrode structural integrity, a stable solid electrolyte interphase and ultra-fast electronic transport. As a result, the 8 h RP@Ni–P composite presents a super high capacity (1256.2 mA h gcomposite−1 after 200 cycles at 260 mA gcomposite−1), superior rate capability (491 mA h gcomposite−1 at 5200 mA gcomposite−1) and unprecedented ultralong cycle-life at 5000 mA gcomposite−1 for an RP-based SIB anode (409.1 mA h gcomposite−1 after 2000 cycles). This simple scalable synthesis approach will provide a new strategy for the optimization of core@shell nanostructures, paving the way for mass production of high performance electrodes for SIBs and other energy storage systems.